Bar code scanner laser radiation exposure limit control system
First Claim
1. In a code symbol scanner apparatus having a laser normally operable at a power output above radiation safety limits and photodetector means for deriving signals from said code symbols, the improvement which comprises mode control means for providing a first mode of operation of said apparatus during which a search is carried out for said code symbols and a second mode of operation after said symbols are detected and while scanning of said symbols is carried out, means for operating said mode control means for initiating said second mode upon detection of a first of said symbols, means for discontinuing said second mode unless signals corresponding to successive ones of said symbols are derived by said photodetector means within a given period of time, means operated by said mode control means for turning on said laser during said first and second modes at said power output above said limits, and means for further controlling said mode control means for controlling the time said laser is turned on so that the radiation safety limits are not exceeded.
5 Assignments
0 Petitions
Accused Products
Abstract
In order to meet the requirements for laser radiation safety, namely laser output which can enter the naked human eye indefinitely and cause no discernible damage (Class I emission limit) in a code symbol (bar code) scanner, a mode controller is used for generating a laser enabling the signal so as to turn the laser on in a search mode until the symbols are acquired and in an in-code mode while the symbols are being scanned. When the laser is turned on it operates at a power output which would exceed the Class I emission limits if operated continuously. Circuitry is provided for operating the mode controller so that the laser is not enabled to turn on for a period long enough to exceed Class I limits. Such circuitry may be an integrator or accumulator which responds to the time that the mode controller turns the laser on and which provides an output for inhibiting the mode controller from turning the laser on for a period of time sufficient to prevent the Class I emission limit from being exceeded. The circuitry may alternatively be a pulse generator which permits the mode controller to turn the laser on repetetively during a "find paper" mode with a duty cycle such that the Class I emission limits are not exceeded.
147 Citations
9 Claims
- 1. In a code symbol scanner apparatus having a laser normally operable at a power output above radiation safety limits and photodetector means for deriving signals from said code symbols, the improvement which comprises mode control means for providing a first mode of operation of said apparatus during which a search is carried out for said code symbols and a second mode of operation after said symbols are detected and while scanning of said symbols is carried out, means for operating said mode control means for initiating said second mode upon detection of a first of said symbols, means for discontinuing said second mode unless signals corresponding to successive ones of said symbols are derived by said photodetector means within a given period of time, means operated by said mode control means for turning on said laser during said first and second modes at said power output above said limits, and means for further controlling said mode control means for controlling the time said laser is turned on so that the radiation safety limits are not exceeded.
Specification